A warm-air oil-fired heater with a 100,000 BTU output is available. This is large enough to heat a 25-foot-long greenhouse. The heater is 23 inches high, 72 inches long and 22 inches deep, and is designed to fit underneath a greenhouse bench. The gun-type oil burner comes equipped with all controls, and a special thermostat with sunshade. The built-in blower has a rating of 900 cubic feet per minute, to assure good air circulation. A masonry chimney 12 to 24 inches above the ridge, or a metal smoke pipe with rotary cap to help provide adequate draft, should be provided. Standard household fuel oil can be used. If the heater is installed in an attached workroom, a return air duct is required.